Lighting is on most commuters' minds as we lose DST and the days get shorter. There are a couple of ways to go about properly lighting a bike, and each has its proponents.
Generators: My main commuter bike has a generator hub and permanently installed lights. I like this option because I can grab the bike at any time and ride without having to hook up lights, worry about batteries, or worry about not having lights. The downside is that there is less variety in the style of lighting than with battery-powered and I have to be careful about where I park since I can't remove the lights to avoid theft.
Rechargeable: I used to have a NiteRider TrailRat on my MTB; the light was stolen along with the bike a few years ago. This style of light, with the rechargeable power cell, is a good compromise between the smaller battery lights and the larger generator lights. They are removable (which has pros and cons) and have to be charged.
Battery: The smaller lights, mostly in the "to be seen" category. Most serious cyclists have a few different options floating around. I have more tail lights than headlights. Some are powerful but not if you're riding in the black or fast.
Flashlights: A final option some people go with is strapping a flashlight to the bars. This is especially useful if you don't want to buy bike-specific lighting or plan to do some hacking and build your own system.
And then there's this:
The Polarion PH50's ergonomic design was specifically developed to meet the mission requirements of Law Enforcement and Military personnel in the field. The Polarion PH50 draws it namesake from the power and intensity of the sun. This 50-watt powerhouse features a High Intensity Discharge (HID) arc lamp emits an incredible level of blinding white light ~ 5,200 lamp lumens.
Yeah, that says 5,200 lumens. In comparison, the NiteRider SlickRock, which they describe as "just about the brightest bike light available" comes in at about 920 lumens
The downside to all that power? It'll set you back $2,395. To really appreciate the power of the light check out some of the pictures on the Polarion website.